i think gulfair fly from dammam to doha via manama short hops about 20 mins each flight if transiting you wont need a visa but if visiting doha you will get visa on arrival at 100 riyals

This is correct - hop over the causeway and get a flight from Manama.

I think the visa fees have gone up but check online. You can only pay by credit card. Hotels can arrange visas for you. The cheapo hotels are down in Umm Gawlina not far from the airport arrivals terminal.